Method of preparing a super absorbent polymer and a super absorbent polymer prepared therefrom

Abstract

A method of preparing a super absorbent polymer (SAP) includes the steps of preparing a first hydrogel polymer by carrying out a thermal polymerization or photo polymerization of a monomer composition including a water-soluble ethylene-based unsaturated monomer and a polymerization initiator; preparing a second hydrogel polymer by carrying out a thermal polymerization or photo polymerization of a monomer composition including a water-soluble ethylene-based unsaturated monomer and a polymerization initiator; drying and milling the first hydrogel polymer and distributing the first hydrogel polymer into a fine powder having a particle diameter below 150 μm and a base resin having a particle diameter of 150 μm to 850 μm; fabricating a reassembled body of the fine powder by mixing the fine powder and the second hydrogel polymer; and mixing the reassembled body of the fine powder with the first hydrogel polymer, and drying and milling the same.

What is claimed is: 
     
       1. A method of preparing a super absorbent polymer, including the steps of:
 preparing a first hydrogel polymer by carrying out a thermal polymerization or photo polymerization of a monomer composition including a water-soluble ethylene-based unsaturated monomer and a polymerization initiator; 
 preparing a second hydrogel polymer by carrying out a thermal polymerization or photo polymerization of a monomer composition including a water-soluble ethylene-based unsaturated monomer and a polymerization initiator; 
 drying and milling the first hydrogel polymer and distributing the first hydrogel polymer into a fine powder having a particle diameter below 150 μm and a base resin having a particle diameter of 150 μm to 850 μm; 
 fabricating a reassembled body of the fine powder by mixing the fine powder and the second hydrogel polymer; and 
 mixing the reassembled body of the fine powder with the first hydrogel polymer, and drying and milling the reassembled body of the fine powder mixed with the first hydrogel polymer, 
 wherein the second hydrogel polymer has higher water holding capacity than the first hydrogel polymer. 
 
     
     
       2. The method according to  claim 1 , wherein the first hydrogel polymer has the water holding capacity of 30 to 50 g/g and the second hydrogel polymer has the water holding capacity of 35 to 60 g/g. 
     
     
       3. The method according to  claim 1 , wherein the second polymer has higher water soluble component content than the first polymer. 
     
     
       4. The method according to  claim 3 , wherein the water soluble component content of the first polymer is 5 to 30 weight % and the water soluble component content of the second polymer is 6 to 35 weight %. 
     
     
       5. The method according to  claim 1 , wherein the second hydrogel polymer is in a free-swollen state with water. 
     
     
       6. The method according to  claim 5 , wherein the second hydrogel polymer is free-swollen with water so as to contain about 50 to about 50,000 weight % of water based on the weight of the second polymer. 
     
     
       7. The method according to  claim 1 , wherein the step of fabricating the reassembled body of the fine powder is carried out by mixing 10 to 200 parts by weight of the second hydrogel polymer with 100 parts by weight of the fine powder. 
     
     
       8. The method according to  claim 1 , further including a surface crosslinking step after the step of drying and milling the reassembled body of the fine powder and the first hydrogel polymer. 
     
     
       9. A super absorbent polymer, prepared by the method of  claim 1 . 
     
     
       10. The super absorbent polymer according to  claim 9 , having the water holding capacity of 20 to 50 g/g when it is measured according to EDANA method WSP 241.2. 
     
     
       11. The super absorbent polymer according to  claim 9 , having the penetrability of 200 seconds or less. 
     
     
       12. The super absorbent polymer according to  claim 9 , wherein the content of the fine powder of which the particle diameter is below 150 μm is 5 weight % or less.